Want a Quick Win? Secure your DNS

Share

 

Ransomware is currently the number one form of cyber attack due to its profitability and simplicity in execution. It is now evolving as a business model where any ‘Joe Bloggs’ can buy ransomware code for a monthly fee – ransomware as a service. Ransomware thrives partly because of bitcoin and the associated anonymity of attackers who get paid via an untraceable cryptocurrency transaction. The stages of a typical ransomware attack include;

 

  • Stage 1 – Infection

Ransomware always starts with some host infection of malware via phishing attacks, or a website hosting malware

 

  • Stage 2 – Command and control setup stage

This handles the key exchange process to encrypt the files on the infected host

 

  • Stage 3 – Extortion stage

Payment of the ransom and then ‘hopefully’ getting the key to decrypt the encrypted files.

 

Ransomware is constantly evolving and not being breached yet is no guarantee that it won’t happen in the future.

 

Many organisations are using hope and anonymity as a risk mitigation strategy against ransomware – assuming they are small and have not been attacked yet. The fact is that the supply chain is now an increasing focus of malware attacks as a means of accessing valuable data through the back door of larger enterprises.

 

 

Anti-Ransomware Best Practices

 

As with every effective security approach you need a policy and a risk assessment of the threats so this is a given before we get into the type of approach and solutions that need to be in place. Please see some of our previous blogs or check out the NCSC website for some invaluable resource.

 

Phishing can be very sophisticated making it hard to tell if a link is bad or not. Effective protection cannot rely solely on end users, it must be engineered into the system with the right protection mechanisms correctly configured.

 

To start off with you need good anti-spam, anti-phishing and web controls to control the Internet traffic, this could be incorporated into a good endpoint protection solution. Use an email and malware analysis gateway to inspect executables for malware. The gateway should be configured to block files if there is any doubt about it’s authenticity. It is better to stop/delay web downloads so that they can be inspected and properly classified than to run the risk of infection.

 

78% of attacks exploit phishing so it is a good thing to correlate known exploits to the vulnerabilities in your organisation and prioritise patching based on known exploits.

Use network analysis and visibility tools to analyse traffic on the network so you can see what is changing and be alerted to abnormal behaviour.

 

If you do get infected, have effective Backup and DR policies and processes, and ensure that the recovery procedure has been tested and works.

 

DNS Security is the Quick Win

 

92% of cyber attacks make use of DNS at some stage or another through the execution of the attack. DNS is therefore the greatest opportunity to secure your network while having an immediate impact.

 

What if your systems know that a website url a client is trying to access via DNS resolution is a bad site, hosting malware. You could just block it and prevent any interaction with the malware in the first place. This form of protection can be immediate with no impact on client or application performance.

 

A web based infection is usually a 2 step process –  which redirects your web browser to another domain created using an exploit kit which finds a vulnerability in say Flash or Silverlight. The malware will then do a command and control (CnC) call back using DNS resolution to get an encryption key. Until the CnC connection happens there is no damage created.

 

Analysis has shown that most ransomware does a DNS call back, ransomware payment notification also uses DNS. The ability therefore to block a malware connection via DNS security at one or another step of the malware execution process can therefore prove to be the most effective way to implement malware protection.

 

An effective DNS security protection control can have the ability to identify the endpoints attempting the malware connection and therefore feed into the clean-up and mitigation plan.

 

An important service in addition to the above is the ability to query domains and file hashes from a central intelligence platform that has up to the  minute data on the bad domains so that your security incident response team has the ability to conduct intelligent investigations independently of any infections. For instance if you keep doing a DNS query for a site in Russia and you don’t have any business relationship in Russia, that’s something that you should query.

 

Another challenge is the decentralised nature of organisations due to remote working and the increasing importance of branch offices. Mobile devices such as laptops are the primary devices where user changes could compromise security. Around 80% of remote workers disable their VPNs when they browse the web. A DNS based security mechanism can help to maintain the security posture where these remote workers able to still make use of this form of protection even when they disable their VPNs. DNS security can protect any device including IoT, guest devices and roaming clients.

 

Correct implementation of DNS security could make it the first line of defence even before a connection is established by checking the DNS request and blocking bad sites. This will help the IT teams by freeing them up from a large number of alerts that would be generated if the malware had been downloaded.